My imagination was recently captured by an Instructable by a user named Seamster on how to build a wooden marble coaster. Since it looked like it was within range of my very limited woodworking abilities, I decided to attempt building one of my own. The only real sticking point was the spiral screw used to bring marbles to the top of the coaster.
Seamster used a Dremel to hand-carve the screw from a rounded piece of 2x4. I initially tried this with a store-bought wooden dowel, but quickly lost patience with the process (it turns out that I'm far lazier than I thought). I decided to see if I could figure out a faster way to carve out a wooden screw. I quickly hit upon a very simple method. This has probably been done before, but I'll document it here, just in case.
Step 1: Equipment and Material
The only woodworking equipment you will need to do this is:
- a table saw with a decent blade
- a miter gauge (pictured)
- a drill
- a suitable drill bit for your screws
- a clamp
- a screwdriver
- a pencil
...and that's it!
The materials list is equally simple:
- a scrap piece of board 1 to 2 feet long and a couple inches wide
- 3 screws (2 of these will need to fit the holes in your miter gauge)
- a wooden dowel to carve
Step 2: Make the Jig
The secret to making this process easy and accurate lies in this simple jig. It provides a guide for the dowel to keep it straight and to control how it moves during the carving process.
And, if the term "jig" calls to your mind the same nightmarish, complicated contraptions that it does to mine, then relax. I really do mean simple.
First, set your miter gauge to your desired angle. This will determine the angle of the spiral you cut. I found that setting my gauge to 60 degrees worked well.
Second, select or cut a piece of wood long enough to span from your miter gauge to about 6 inches past the table saw blade. It should be at least as wide as your miter gauge is tall and should be at least an inch taller than the tale saw blade setting you use (see the next step).
Third, attach this guide to your miter gauge. Your miter gauge should have holes in it specifically for attaching things like this to it. Just lay the wooden guide against the gauge where you want it and use a pencil to mark the location of the gauge holes. Drill matching holes and attach the guide to the gauge with suitable screws.
Step 3: Set the Blade Height
You'll need to set the blade height to get your desired thread depth. I didn't do any measuring and eyeballed a setting and went with it.
Different settings will produce different results. Specifically, setting the blade to reach higher than the middle of the dowel will produce more of a spiral than a screw. I haven't had luck with this yet, but, with patience it should be possible.
Step 4: Place the Guide Screw
I found it better to add a screw to the jig to keep the dowel moving evenly throughout the carving process. If you have a steady hand and nerves of steel, you could, potentially, skip this step.
Place the dowel against the jig and align it with the saw blade as shown in the first picture. Push the jig into position so that the dowel is over the middle of the blade. You will want to clamp it into place, if possible, to keep the miter gauge from sliding around.
This part is potentially tricky, but shouldn't be too hard and only needs to be done once.
Carefully and slowly turn the dowel toward you. You will find that the dowel will naturally slide to the right as it turns because the blade will continue to follow the groove it is making as it cuts (see picture 2). It should, theoretically, be possible to let this process continue as you carve the rest of the dowel, but it is difficult to keep it accurate.
Keep turning until the dowel has almost completed a full rotation and the starting point of the groove meets the jig (see picture 3).
To help guide the rest of the carving, you will need to put a screw here where it will fall into the groove created by the blade. make a pencil mark where the groove meets the jig (picture 4).
Select a screw that has a diameter slightly smaller than the kerf (width) of the blade, drill a hole for it at the pencil mark, and screw it in to the jig so that the tip extends into the groove in the dowel (picture 4). As you continue to carve the dowel, this screw will guide the movement of the dowel to keep the spiral cut even.
Step 5: Continue Cutting
Make sure to, again, clamp the miter gauge in place (picture 1), to keep it from sliding and changing the cut depth.
Continue rotating the dowel toward you, allowing it to move to the right, guided by the screw running through the groove. Go slowly and carefully and watch your fingers!
Step 6: Widen the Groove If Desired
The groove can be made as wide as you want by adjusting the placement of the dowel on the jig and repeating the carving. Take your time and go slowly.
Step 7: Cleanup and Enjoy
Cleanup the cuts with sandpaper and you're good to go.
This method is not very difficult, and produces some great results. Hopefully, this idea will be useful to someone and I would love to see what you do with it. Please include any photos of your end results in the comments below!
KellyCraig made it!